Atrial fibrillation vs atrial flutter: how the two rhythms differ

The heart's beat is controlled by an electrical system that makes the upper chambers (the atria) and the lower chambers (the ventricles) work together. Atrial fibrillation and atrial flutter are both disturbances of the electrical activity in the atria.

The practical difference is the pattern. The BHF says atrial fibrillation happens when the electrical signals in the upper chambers are not sent out properly. They should be steady and regular, but instead they quiver or twitch, so the heart beats randomly and does not pump blood as well as it should. In atrial flutter, it says, the usual electrical pathway is interrupted and a new, smaller faulty pathway forms in the atria. Because that pathway is so small, the impulses travel very quickly around the atria, so they beat much faster than they should, at around 300 beats per minute. The ventricles cannot keep pace with the atria, so the upper and lower chambers beat at different speeds.

The table brings together what the NHS and the British Heart Foundation say about each condition.

You cannot reliably tell the two apart from how they feel. Both can cause the sensation of the heart pounding, racing, fluttering or skipping beats. The NHS lists the main symptoms of atrial fibrillation as an irregular pulse, sudden palpitations lasting seconds to minutes, a heartbeat faster than 100 beats per minute, tiredness, finding it harder to exercise, chest pain or tightness, and breathlessness or dizziness. The BHF lists for atrial flutter palpitations, shortness of breath, tiredness, light-headedness, fainting and chest tightness, and notes that people with flutter often have no symptoms at all.

The NHS also says that some people with atrial fibrillation have no symptoms and it is found during a routine check-up or tests for something else. Whichever rhythm it is, the NHS advice is to see a GP if you think you may have symptoms or have palpitations that keep happening or are getting worse.

A fast or irregular heartbeat combined with certain other symptoms is an emergency. The NHS says to call 999 if you currently have a fast or irregular heartbeat and any of: chest pain, shortness of breath, sweating, feeling or being sick, fainting, dizziness or falling over, a severe headache, weakness or numbness on one side of the face or body, blurred vision or loss of sight, or confusion or difficulty speaking.

The distinction is made from a recording of the heart's electrical activity, usually an electrocardiogram (ECG). Because atrial fibrillation is irregular and atrial flutter is regular, a cardiologist or other clinician can name the rhythm from the tracing; this is why the pulse pattern alone, which can feel similar, is not enough.

The BHF says that for atrial flutter your doctor should recommend an ECG or a Holter monitor test, that you may need more than one ECG because the flutter does not always show up, and that you might have an implantable loop recorder fitted under your skin to record electrical activity over a longer period. The NHS says that when atrial fibrillation is suspected you will be referred to a cardiologist and tests may include an ECG, an echocardiogram, a chest X-ray and blood tests.

Because the rhythms come and go, a normal ECG in the clinic does not rule either out. That is the reason longer recordings are used when symptoms are intermittent.

The treatments overlap. For atrial fibrillation, the NHS says you may be given medicine to control the rate and rhythm of the heart, such as beta blockers, and anticoagulants to lower the risk of blood clots or stroke. Other options include ablation, electrical cardioversion, or a pacemaker or implantable cardioverter defibrillator. Sometimes atrial fibrillation is caused by another health condition or medicine, and treating that or stopping the medicine can improve symptoms.

For atrial flutter the BHF says treatment may include medicines to control heart rate such as beta blockers, calcium channel blockers and other anti-arrhythmic medicines, cardioversion, and ablation. Flutter can change the way blood moves through the heart and lead to a clot that breaks off and causes a stroke, so you may need an anticoagulant such as warfarin or a NOAC. Left untreated, the BHF says atrial flutter can weaken the heart over time and cause heart failure.

Which treatment suits which person is a decision for the treating cardiologist. The BHF notes that it is possible for atrial flutter to go away after treatment but it may return, in which case follow-up with your doctor is needed.

The NHS says that there is currently no cure for atrial fibrillation, but treatment should help manage symptoms and lower the chance of complications such as blood clots, stroke and heart failure. It advises avoiding triggers such as caffeine, spicy food, stress, dehydration and lack of sleep, keeping to a healthy weight, being active, not smoking, and not drinking too much alcohol. It also says to avoid intense exercise or exercising when you have symptoms, and that you may need to tell the DVLA if you drive.

The BHF says that with treatment people with atrial flutter should be able to continue doing what they enjoy, although it can take time to learn the triggers. Both pages acknowledge the emotional impact: the BHF says you may feel more anxious or stressed than normal after the diagnosis and suggests talking to loved ones and your GP.